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https://issues.apache.org/jira/browse/YUNIKORN-3243?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shubham Mishra updated YUNIKORN-3243:
-------------------------------------
Description:
When two sibling queues under the same parent have vastly different guaranteed
resources (e.g., 3600:1 ratio), the fair-share queue sorting in {{TryAllocate}}
causes the smaller queue to be completely starved — its {{app.tryAllocate()}}
is never called. This has two consequences:
# {*}Scheduling starvation{*}: The smaller queue's asks are never evaluated
for allocation, even when nodes have capacity.
# {*}Autoscaler blindness{*}: Because {{SetSchedulingAttempted(true)}} is only
set inside {{app.tryAllocate()}} (line 1035 of {{{}application.go{}}}), the
starved queue's asks never get this flag. {{inspectOutstandingRequests}} skips
them, so the cluster autoscaler (e.g., Karpenter) is never notified that
capacity is needed.
The second issue is the more critical one — even if scheduling is delayed, the
autoscaler should be able to provision nodes in parallel. But with the current
design, the autoscaler signal is gated on queue visitation.
Here are the unit-tests to reproduce this -
https://issues.apache.org/jira/browse/YUNIKORN-3243
h3.
was:
When two sibling queues under the same parent have vastly different guaranteed
resources (e.g., 3600:1 ratio), the fair-share queue sorting in {{TryAllocate}}
causes the smaller queue to be completely starved — its {{app.tryAllocate()}}
is never called. This has two consequences:
# {*}Scheduling starvation{*}: The smaller queue's asks are never evaluated
for allocation, even when nodes have capacity.
# {*}Autoscaler blindness{*}: Because {{SetSchedulingAttempted(true)}} is only
set inside
{{app.[tryAllocate|https://github.com/apache/yunikorn-core/blob/master/pkg/scheduler/objects/application.go#L1029]()}}
(line 1035 of {{{}application.go{}}}), the starved queue's asks never get this
flag. {{inspectOutstandingRequests}} skips them, so the cluster autoscaler
(e.g., Karpenter) is never notified that capacity is needed.
The second issue is the more critical one — even if scheduling is delayed, the
autoscaler should be able to provision nodes in parallel. But with the current
design, the autoscaler signal is gated on queue visitation.
h3.
> Fair-share queue sorting causes starvation of sibling queues with asymmetric
> guaranteed resources
> -------------------------------------------------------------------------------------------------
>
> Key: YUNIKORN-3243
> URL: https://issues.apache.org/jira/browse/YUNIKORN-3243
> Project: Apache YuniKorn
> Issue Type: Bug
> Reporter: Shubham Mishra
> Assignee: Shubham Mishra
> Priority: Major
>
> When two sibling queues under the same parent have vastly different
> guaranteed resources (e.g., 3600:1 ratio), the fair-share queue sorting in
> {{TryAllocate}} causes the smaller queue to be completely starved — its
> {{app.tryAllocate()}} is never called. This has two consequences:
> # {*}Scheduling starvation{*}: The smaller queue's asks are never evaluated
> for allocation, even when nodes have capacity.
> # {*}Autoscaler blindness{*}: Because {{SetSchedulingAttempted(true)}} is
> only set inside {{app.tryAllocate()}} (line 1035 of {{{}application.go{}}}),
> the starved queue's asks never get this flag. {{inspectOutstandingRequests}}
> skips them, so the cluster autoscaler (e.g., Karpenter) is never notified
> that capacity is needed.
> The second issue is the more critical one — even if scheduling is delayed,
> the autoscaler should be able to provision nodes in parallel. But with the
> current design, the autoscaler signal is gated on queue visitation.
> Here are the unit-tests to reproduce this -
> https://issues.apache.org/jira/browse/YUNIKORN-3243
> h3.
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